


Sins of the Sea

by CreativeSweets



Category: Yuri!!! on Ice (Anime)
Genre: Anal Gaping, Animal Instincts, Breathplay, Breeding, Claiming Bites, Come Inflation, Eggpreg, Eggs, Exhibitionism, Not a kid fic, Nymphomania, Other, Overstimulation, Oviposition, Possessive Behavior, Pregnant Sex, Public Sex, Ritual Public Sex, Rough Sex, Shota, Tentacle Sex, Threesome, Underage at a Glance, Yuuri gets railed by tentacles, mer Victor
Language: English
Status: Completed
Published: 2018-07-18
Updated: 2019-04-28
Packaged: 2019-06-12 09:07:35
Rating: Explicit
Warnings: Underage
Chapters: 3
Words: 3,257
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15336528
Author URL: https://archiveofourown.org/users/CreativeSweets/pseuds/CreativeSweets
Summary: "Wait!" Yuuri screeches, hands flailing to grip the retreating tentacles, "What's…what's your name?"The Ocean calls me Vit'irhudael.------------------In which Yuuri's an oceanid—a sea nymph—that gets saved by a tentacle daemon.





	1. Chapter 1

**Author's Note:**

> Okay, so that Underage at a Glance tag: Basically, Yuuri's nearly 200 years old, but has the physical appearance of a young boy. Hence the archive warning. If this bothers you, there's a back button.
> 
> Before anyone asks, I am _intentionally_ vague with Yuuri's appeared age. Therefore, feel free to take creative liberties with it.
> 
> Anyways! Please enjoy~

Yuuri perches on the edge of the cliff overlooking his beach, resting his chin on his knees, arms wrapped securely around his legs. It's the height of summer, the screeches and calls of the humans scurrying along pierce the salty air. He watches the colorful blobs move with a disinterested gaze.

After being on this beach for nearly 200 years, there's not much that surprises him anymore. He sighs. Maybe he should sleep for a year or so and then things might be different. Standing up, he stretches his arms over his head and groans at the pull in his muscles.

A strong wind picks up and his foot slides off the edge of the cliff.

And then he's falling, falling,  _ falling  _ towards the deep ocean below him. The fall won't kill him, but he does hope that he misses the majority of the sharp rocks at the bottom. Healing takes a lot out of him. He takes a deep breath and prepares for the familiar sting of the ocean.

Only it doesn’t come.

He's surprised when thick, slick  _ tentacles  _ wrap around his torso and pull him into a tight embrace.

_ Hush now, Little One,  _ he hears a voice in his head say,  _ you are safe now. _

He holds back a snort; it's clear this tentacle daemon thinks he's how he appears: an innocent little boy.

The cool, ocean-temperature tentacles make goosebumps form along his skin and he fights his initial response to struggle. They  _ grip  _ just a little harder as the daemon starts moving towards the shore.

His feet touch the warmed sand and those tentacles start sliding off of him, leaving wetness behind.

_ You are safe now,  _ the daemon repeats,  _ please be more careful in the future. _

"Wait!" Yuuri screeches, hands flailing to grip the retreating tentacles, "What's…what's your name?"

_ The Ocean calls me Vit'irhudael. _

Vit'irhudael.

There's no way Yuuri  _ won't  _ give the daemon a nickname. Just like how there's no way he won't let the daemon fade back into the ocean. He grips the retreating tentacles. There's a binding spell he knows, learned from his sea-witch friend Phichit. There's no better time than the present to test it out.

He licks his lips, keenly aware of the humans that walk the beach that could stumble upon them. All part of the ritual. Placing the tentacles back on him, he fumbles to reach a sharp enough shell on the beach.

"Well,  _ Vit'irhudael,"  _ Yuuri says slowly as he finally nicks his fingers when they skim a sharp shell, "I look forward to being your Master."

He brings his bloody fingers down sharply onto a thick tentacle, smearing blood with a wet  _ smack _ .

"I, Katsuki Yuuri, Oceanid of Hasetsu Bay, hereby claim the Ocean's tentacle daemon Vit'irhudael as a loyal servant of mine in the name of Our Sovereign Lady Chihoko." The tentacles swirl and tighten their grip around him. He continues, "As such, the daemon shall act in its natural capacity as a guardian until the time I die, or until I deign to release it from service."

Lights flash from within the tentacles, a physical manifestation of his Oath. Yuuri knows what needs to happen next—in theory. Phichit was unhelpfully vague when he talked Yuuri through the ritual.

_ ("Don't worry, Yuuri," Phichit said as he winked, "It'll be obvious what needs to happen after the Oath takes hold in the daemon.") _

Yuuri waits anxiously as the tentacles curl underneath his clothes and at the first  _ rip  _ he pieces together what Phichit meant.

He's going to get fucked by the tentacle daemon.

He hums with satisfaction as they lift him off the sand and spread him open, thick slime tingling hotly on his sun-kissed skin. A tentacle curls around his neck and he opens his mouth in invitation—one that doesn't go ignored—and soon he's moaning around one, his tongue running along the suckers. He closes his eyes and just  _ feels. _

Feels the sun warming the slick covering his body. Feels the way a thin tentacle twirls around his hard member. Feels the blunt pressure at his entrance. Feels the suction of the suckers on his chest, his legs, his arms.

He cries out at the stretch as a tentacle pushes into him. It's so big—and without preparation—he shudders at the burn and tears form in the corners of his eyes. But  _ god,  _ does it feel so good. A pleasant pain-pleasure that he knows only a tentacle daemon can give him.

He shoots a quick thanks up to whatever deity was overseeing the wind atop the cliff today that knocked him over.

His throat constricts against the intruding tentacle and in response the one wrapped around his throat tightens. He jerks against his living restraints as his breaths grow shallower and he feels like he's floating. There's a blissful moment that he believes he's going to pass out, but it's overshadowed by the pleasure traveling down his spine all the way to the tips of his toes. The tentacle leaves his mouth and he gasps for air. He watches through his heavy lidded gaze as the tentacle wrapped around his cock works him through his orgasm, his cum mixing in with the thick slick on his stomach.

He closes his eyes as the tentacles stutter and release over him, sealing the binding spell in place.


	2. Chapter 2

Yuuri's on edge—all the sea creatures are. Not only is the summer solstice coming, but this year the full moon coincides with it. Meaning it's a bad time to be in or around the ocean if you aren't preternaturally inclined.

For Yuuri, he prepares as usual, but with more enthusiasm thanks to his new  _ companion  _ he has. The air is tinged with excitement as he meticulously makes sure his cove is clean and will allow the most moonlight to filter in once the sun sets. Vit'irhudael—whom Yuuri has lovingly nicknamed  _ Vicchan— _ sits impassively right at the water's edge. But he can tell the daemon is just as excited as he is; the faint blue lights, the manifestation of Yuuri's Oath, flicker with increasing intensity as Yuuri's amorous mood affects him.

As the violent crimson colored sky fades to a deep blue-black the area is filled with the bright light of the full moon. Yuuri's skin tingles and he watches the waves swell and rise.

Vicchan wastes no time and wraps him up in his tentacles. His normal semi-viscous slick he produces is now thick and creamy—the natural chemicals from the full moon turning it into more of an aphrodisiac. It leaves hot trails along his skin that leave him panting into the warm night. By the time Vicchan has all his tentacles on him, he's already a wreck—face flushed and cock weeping.

At the first brush of a tentacle against his member it leads to his first orgasm of the night—the first of many. After all, the Moon has placed Her children into the sea to become Her eyes and ears, and, during the full moon, Her flesh to experience the world. As such, Yuuri is extremely thankful for the daemon's presence.

A tentacle brushes his hair back from his face and he chases the touch with a whimper. When he opens his mouth to beg for more, Vicchan's one step ahead of him and forces a tentacle into his mouth, prodding at the back of his throat. Relaxing his throat, he groans as he feels the twitching—the only warning he gets before he tastes the sweet, yet salty, release. Swallowing what he can, he mourns the loss of the drops that dribble down his chin as the tentacle leaves his mouth.

It's quickly replaced by another and Yuuri moans at the stretch. He gasps as the tentacle that was sliding across his ass breaches him. Warmth seeps into his skin as more slick is spread across his skin. A second tentacle stretches past his tight rim and tears prick his eyes another orgasm ripples through his body.

It's too much. It's not enough. He stares down at his distended belly, the two tentacles pushing against his insides. More tentacles around his midsection press against his sensitive swell and an obscene moan is pulled from him.

Suckers pull on his nipples and Yuuri closes his eyes as his body is taut and humming in the moonlight. There are  _ so many  _ tentacles on him—so many trailing up his sides, rubbing more slick along his heated skin. He whines as the one leaves his throat to finish over his face and chest. A third tentacle prods innocently where the other two are in him and his breath catches.

"Wait, no," he cries out, "there's no way I can take that, Vicchan,  _ please. _ "

The daemon doesn't heed his pleads and the third tentacle blindly pushes in, spreading him even wider. He looks…almost  _ pregnant. _

_ "Ahh!"  _ Yuuri screams as he cums from the burning stretch. His whines reach a fevered pitch as he's pried and fucked open.

A faint  _ splash  _ near the mouth of his cove has him snapping his head towards the sound. Surely no-one in their right mind would dare intrude. But right there, with only a head and shoulders visible, is the most beautiful mer Yuuri's ever seen: silver strands fanning out in the water around him, bright crystalline eyes watching him, a blush high on those sharp cheekbones. Yuuri moans louder as the tentacles rub against his insides, his unexpected audience hurtling him towards another orgasm.

He looks back at the mer who's clinging to the rocks. At those flushed cheeks and slightly parted lips. Clearly this mer had no mate, otherwise they wouldn't be  _ here,  _ not during a full moon. He makes his mind up rather quickly.

"Vicchan," Yuuri gasps out as the daemon notices their little voyeur, "we can't just leave him. He's probably suffering so much."

Yuuri remembers his first full moon. All alone, he had to pleasure himself for the Moon as his instincts demanded. He only lasted half the night before exhaustion left him panting and dissatisfied with his inability to give a proper offering. He wouldn't wish that upon any sea creature.

_ Master?  _ Vicchan asks him,  _ You would like to help the mer? _

A whine bubbles up and out of him before he could stop it.  _ "Luna, yes!" _

His eyes lock with pale blue ones before he's unceremoniously flipped around and presented to the mer. Tentacles slide out of him and spread his cheeks to expose his gaping hole. A low rumble from the mer has Yuuri shivering and arching his back to put himself more on display. He looks over his shoulder just in time to see those webbed hands grab at his small, shapely hips. The mer sheathes himself in Yuuri in one quick, feral thrust.

Yuuri's mouth opens in a silent scream as the mer buries himself deep inside his well-fucked hole. His thighs tremble in Vicchan's hold as a tentacle works its way towards his hole in between the mer's thrusts.

His wails echo off the cove walls as the tentacle pushes in, stretching him out even further. His whole body is tingling as he swallows down another tentacle. He loses track of time, only aware that it is passing through the orgasms wrung out of him, the stuttering of the mer's hips, and the exchange of tentacles in both his mouth and his ass. Vicchan brings him out of his moon haze with a simple statement.

_ It is time, Master. _

The moon must be at Her peak then. He whines as the mer pulls out and desperately tries to keep all the spilled cum inside him. It dribbles quickly down his thighs and he locks eyes with the mer as Vicchan moves behind him. His eyes flutter closed when Vicchan's breeding tentacle brushes up against him—thicker and less flexible than the other tentacles. It pushes in slowly and steadily, not stopping until it goes deep, deep inside him.

He's a twitching, panting mess by the time the first egg starts to work its way through the tentacle into him. The first egg settles easily—the second, third and fourth do as well. Gasping at the fifth egg being stuffed into him, he remembers to breathe as his stomach swells and stretches to accommodate.

Hands rub along his growing stomach and he opens his eyes to see the mer staring at it with a look of awe. When the mer's eyes meet his again, he feels the telltale pricks of the mer's nails dig into his skin, possessiveness clear in his face and actions. It sends a shiver down his spine as more eggs are pumped into his body. He's lost count at this point, but nothing else matters asides from the feeling of fullness, the tentacles rubbing along his skin, the mer hovering and touching him.

Yuuri cries out when the mer pinches his nipples, spasming against Vicchan and in turn shifting the eggs inside him. Groaning, he's relieved when Vicchan starts to pull out. Before he can blink, the mer is filling him back up, his grip bruising on Yuuri's hips. As the mer pushes inside him over and over, Yuuri whines as the eggs get shoved further in. He can't control the spasms that overcome his body as it's stretched to its limit, as his body fights to keep the eggs inside when the mer draws all the way back before slamming in again.

He arches his back as the mer's release fills the spaces left inside him. Looking up at the full moon watching over them, Yuuri smiles dreamily as the buzzing under his skin is satiated for now.


	3. Chapter 3

**Notes for the Chapter:**

> A quick note: if you suffer from thalassophobia, there is a small paragraph that has the potential to be triggering. This paragraph can be skipped without missing any vital information.

A long moan finds its way out of Yuuri’s mouth. His newest _guest_ certainly knows how to fill him up. It’s not the best—Vitya has that spot—but it’s certainly enough to leave him satisfied for at least a little bit. Yuuri wiggles against where he’s pinned against the shallow bank in his cove. It makes his guest grind into him further, causing cum to squish and drip out of him. Squeaking at the suddenness, Yuuri nearly asks his guest to stay longer, fill him up more, as his neck is nibbled on.

Opening his eyes, Yuuri’s gaze immediately locks onto the lone mer that just entered his cove—Vitya—and a hot spike of lust surges through him. A harsh nip to his neck makes him gasp. In an instant Vitya is in front of him, eyes glinting dangerously in the reflected sunlight. Yuuri doesn’t even feel bad when the warm body covering him gets ripped off him, when cum trickles out faster down his legs. Not when Vitya, in all his furious splendor, looks like a mer possessed. Not when Vitya grips him _hard_ and growls low. Not when Vitya spits out an aggressive trill, an unequivocal _Mine._

Sharp teeth puncture Yuuri’s lips and he moans as he starts to trail his hands over Vitya’s shoulders. Suddenly his hands are thrown off, Vitya backing up just enough to grip his hips and drag him further into the water, enough that when Vitya’s fingers enter him, the cum floats out into the water. Yuuri squirms with the different position. Apparently dissatisfied with how slow the process is, Vitya removes his fingers, much to Yuuri’s disappointment, only to cry out as Vitya’s long, rough tongue enters him.

Blissed out, Yuuri loses track of time as he’s eaten out, as Vitya’s claws grip his twitching thighs, as Vitya periodically stops and bites his inner thighs. It’s only when his hole is raw and puffy, now empty, that Vitya finally stops assaulting him, shifting back. As Yuuri tries to catch his breath from the not-so-unwelcome attack, he watches Vitya with confusion through his half-lidded eyes. He twitches under the intense scrutiny he finds in those piercing blue eyes.

Just as suddenly as he was let go, he’s grabbed again, Vitya’s claws digging into his wrists as he’s hauled out of his cove. Yuuri has half a mind to call Vicchan, who simply observed the whole exchange with as much ambivalence as a daemon could. It’s not until he’s being half dragged under the salty waves that he realizes Vitya’s intentions. Thankfully, he’s well equipped to handle being and breathing underwater. However he still sputters and coughs as his body, so used to air, acclimates to water.

Yuuri can’t do anything more than blindly be dragged farther and farther out, until they reach the drop-off, where Vitya suddenly dives, pulling Yuuri into the inky darkness where, twenty seconds of diving later, he’s being pushed into the wall. Except, instead of rock, there’s soft seaweed that sways gently under the rolling waves.

After a disorienting minute where he loses the sense of up and down inside the seaweed-lined tunnel, he’s finally pulled into an opening, lit with bioluminescence from the bloom of jellyfish floating through the area. They flicker when Vicchan enters, no doubt welcoming the daemon.

Sharply, he’s pulled into another area, this one smaller, warmer, and it’s here that the tight grip on his wrists lets go. As he opens his mouth to compliment Vitya’s den, a webbed claw presses against his lips. This claw gently trails along his lower lip, then further down Yuuri’s neck and across his chest. It idly circles Yuuri’s nipples and he closes his eyes at the feeling. Lower, still, and Yuuri pulls in a long breath as his cock twitches when Vitya closes his hand around it.

Yuuri’s eyes flutter open as Vitya’s hand drifts lower and he makes a small trill that seems to ring through the cave. There’s a question here, in the way Vitya holds himself, the way his hands flutter about, the way his swollen member is peeking from his slit, the tilt of his head. There’s a question here, and Yuuri knows his answer.

_“Yes.”_

He’s being manhandled onto a soft bed of sand, his suddenness causing the sand to billow up. Teeth and tongue and fingers all find their way back onto his body and he responds in kind. Vitya’s large cock juts out from him obscenely, deliciously, the viscous pre-cum making it slide easier against his soft skin, to the place that it belongs.

Yuuri throws his head back and moans as he’s spread open and taken. Vitya’s trilling openly now, his joy heard on the sub-harmonics only able to be heard underwater. His rumbling chest presses hard against Yuuri’s, making him gasp and link his arms around Vitya’s neck. It starts with a nip to his ear. And then another right below it. Trailing down his neck. A particularly sharp nip right above the base of his neck. And then one final bite, more harsh and uncaring than the rest, right at the base of his neck.

His orgasm is blinding white light, bursting behind his eyes as he’s bonded to the beautiful mer above, around, and inside him. Vitya stays latched to his neck painfully for a few more brutal surges before he’s stilling, spilling deep inside. Then his sandpaper tongue is lapping at the bite mark— _bond_ mark—to help heal it. Vitya then gathers Yuuri up and snuggles down into the silky sand, pulling Yuuri closer until his tail curls around Yuuri’s back. Yuuri pointedly doesn’t point out that Vitya’s still buried inside him, but instead shifts his leg to a more comfortable position over Vitya.

Yuuri, completely and utterly satisfied, thinks that he could get used to this.

**Author's Note:**

> [tumblr](https://corgispacesiren.tumblr.com/) | [twitter (R18+)](https://twitter.com/corgispacesiren) | [Pillowfort](https://www.pillowfort.io/CreativeSweets)


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